Envelope inserting apparatus is well known and involves inserting paper documents into a waiting envelope that has had its front and rear panels spread apart to receive the insert material. In the inserting station, the envelope arrives first and is typically opened by a combination of devices which may include bending rolls and hold-down fingers. The contents to be inserted then arrive through a second path and are driven into the envelope. Typically, the last part of the inserting motion is accomplished ballistically for about 0.5.degree. to 0.8.degree. using the kinetic energy of the inserts. Reliability problems exist with this system because the envelope does not always open sufficiently, and, due to the bent nature of the envelope, drag is created on the insert material preventing it from reaching the bottom of the envelope.
Apparatus which positively opens the envelope and holds the envelope open, thereby greatly reducing the amount of drag on the insert material and assuring that the insert material is reliably inserted into the waiting envelope, is known from the present applicants' EP-A-0 785 092. In this apparatus, a waiting envelope is supported in a substantially horizontal plane with its back panel situated above its front panel and the envelope flap in its open position and substantially in the plane of the front panel. A pair of hold-down fingers presses the envelope flap from above against the inboard ends of respective pivotable paddles having an interior leg and exterior leg angled out of the plane of the interior leg, to cause the envelope to be arched over a bending roller and the envelope flap to be bowed downwardly. This causes the rear panel to "pop" upwardly. A pair of opening horns are moved between the front and rear panels of the envelope and then raised, thereby opening the envelope ready for an insert or insert collation to be inserted.
In this apparatus, the envelopes are stored with their flaps closed (unsealed) in an envelope supply station. Envelopes are successively withdrawn from this station, each envelope passing along an envelope feed path with its bottom edge leading, its top edge (forming the hinge between the envelope flap and the envelope front panel) trailing and its (closed) flap uppermost. As the envelope passes along the envelope feed path, a flap opening device engages with the envelope flap and bends it back into an open position so that the envelope arrives at the insertion station with its flap open, facing upwardly and trailing. The envelope is arrested at the insertion station and an envelope opening device opens or "throats" the envelope so that a single fed sheet or a collation of fed sheets and optionally one or more inserts can be driven into the waiting open envelope.
In practice, whilst known envelope flap opening devices are effective and reliable, occasionally the envelope flap is not opened for one reason or another. For example, the flap opening device may malfunction, the envelope may not be of appropriate quality, its flap may have previously become sealed due to moisture in the atmosphere or the like, or it may have been originally inserted in the envelope supply station in an incorrect orientation, any of which can then cause the flap opening device to malfunction. Any of these factors gives rise to the intended envelope contents being placed on top of the envelope at the insertion station, and then fed through to a mail collection bin at the exit of the inserter where the sealed envelopes are collected. For obvious reasons, any unstuffed envelope and its overlying contents need to be identified and removed from the stack of prepared envelopes. However, doing this by operator inspection is time-consuming, particularly if, to remedy the situation, the contents are then manually inserted into the envelope and the envelope sealed such as by the operator wetting the envelope flap and sealing it by hand. Furthermore, reliability cannot be certain. If an unstuffed envelope and its overlying contents are not identified and are then fed into a franking machine, they could cause a jam and the contents and the empty envelope would each be treated as a sealed filled envelope and both franked.